Modern technology has allowed the manufacture and use of many medically useful implanted devices. A big advantage to these devices is that there is a continuous contact with physiological fluids and tissues. This contact allows monitors to maintain a constant vigilance on key physiological parameters; pacemakers to correct rhythmic irregularities; and drug delivery implants to keep constant levels of pharmaceutically active compounds in the bloodstream. Implanted devices may also serve structural functions, such replacement hip joints, vascular stents, etc.
Drug delivery implants provide a solution to a number of problems associated with bolus delivery of pharmaceutical agents. Few therapeutic regimen involve administration of a single dose of a selected drug. Instead, most therapies require administration of multiple doses. Where the therapy requires parenteral delivery of the drug, the patient can be subjected to the substantial discomfort and inconvenience of repeated injections. Typically, parenteral drug delivery also requires administration of a bolus of drug in order to provide for an effective drug concentration at the desired treatment site and/or to provide for an adequate systemic levels for an acceptable period of time. Delivery of a drug bolus not only requires delivery of a greater amount of drug, thus driving up the cost of therapy, but can also be associated with undesirable side effects.
One approach for avoiding at least some of the problems inherent in long-term drug delivery involves the use of an implantable drug delivery device. Examples of such implantable drug delivery devices include implantable diffusion systems (see, e.g., subdermal implants (such as NORPLANT#) and other such systems. Alternatively, the implant may be based upon an osmotically-driven device to accomplish controlled drug delivery (see, e.g., U.S. Pat. Nos. 3,987,790, 4,865,845, 5,057,318, 5,059,423, 5,112,614, 5,137,727, 5,234,692; 5,234,693; and 5,728,396). These osmotic pumps generally operate by imbibing fluid from the outside environment and releasing corresponding amounts of the therapeutic agent.
A disadvantage of implanted devices in general is that there is a risk of infection when the device is introduced. Care must be taken during insertion to maintain a clean environment, so that potentially pathogenic microorganisms are not introduced into the body. When delivering drugs to specific sites within the body, it may be desirable to do so through a permanently and fully implanted pump and catheter system. Having the system fully implanted can minimize potential risk of infection because the entire system is located under the skin, minimizing contact with the external environment. Today, the reservoirs of such pump systems are refilled by introducing a needle across the skin and through a silicone septum, and into the drug reservoir of the pump, introducing a possible contaminant pathway to the dry reservoir.
Rather than refilling a reservoir via an external needle, it may be desirable to change out the entire drug reservoir within the body. To minimize the risk of contamination, it is desirable to make this exchange through a closed system. Further, other medical device components, such as batteries in pacemakers, or monitoring cartridges, may also benefit from a closed exchange exchange. The development of such methods would provide a substantial medical benefit.
An implantable drug delivery device is described by Peery et al., U.S. Pat. No. 5,728,396, issued Mar. 17, 1998. Fluid from the environment in imbibed through a semipermeable plug into the water-swellable agent chamber, and the active agent formulation is released through a back diffusion regulating outlet.
U.S. Pat. No. 5,787,900 describes a method and apparatus for loading and reloading a therapeutic drug in an implantable apparatus. The device is further described in U.S. Pat. No. 5,843,069. Refillable drug delivery techniques are described in U.S. Pat. No. 5,798,114.
An apparatus for the delivery of elongated solid drug compositions is described in U.S. Pat. No. 5,837,276. A portable drug delivery system is described in U.S. Pat. No. 5,599,316. A replaceable catheter system is described in U.S. Pat. No. 5,651,767.
Pacemakers and other implantable cardiac devices are well known in the art. For example, see Reynolds et al. (1998) Pacing Clin Electrophysiol 21(8):1646-55, NASPE expert consensus statement: physician workforce in cardiac electrophysiology and pacing. NASPE task force, Washington, D.C.
An in vivo method for repairing a ruptured segment of an implanted device is described by Hogan, et al, U.S. Pat. No. 5,653,759. A guiding catheter and deformable, thermoelastic shape-memory alloy rods are used to access and repair the flawed or failing therapeutic appliance in place.
Replaceable batteries for implantable medical devices are described by Mulier, U.S. Pat. No. 5,314,451. The circuitry for an electromedical device is contained in a hermetic enclosure, while a power supply for the device is contained in a second hermetic enclosure. The two enclosures are coupled together via a multiple conductor lead, which allows replacement of depleted batteries without explanation of the medical device itself. U.S. Pat. No. 4,294,891 provides an intermittently refuelable implantable bio-oxidant fuel cell. Refueling occurs by injection.
The present invention provides a device and method for the closed exchange of a component in an implanted medical device. The exchanger is brought into contact with the implanted medical device in situ. The component is withdrawn from the implanted device and brought into a chamber of the exchanger. Without breaking the contact between implanted device and exchanger, the replacement component is then moved from its position in the exchanger,. and inserted into the correct position in the implanted device. Components of interest for exchange include drug delivery cartridges, e.g. where an expended cartridge is replaced with a loaded cartridge. Also of interest are components such as pacemaker batteries, monitoring devices, and the like.
In one aspect the exchanger features a multi-chambered barrel capable of holding at least one replacement component. After the old component is withdrawn from the implanted device, the barrel is rotated such that the replacement component is brought into position for insertion. The exchanger is optionally provided with a preloaded replacement component.
In another aspect, the exchanger features a multi-chambered barrel, where the replacement component and the expended component are angled to each other, such that each can be inserted or withdrawn through a central contact point without rotation.
In yet another aspect, the invention features a system for maintaining delivery of a drug to a treatment site, where a drug delivery element is a component of the system. The present methods and exchanger provide a means of closed exchange for the drug delivery device component. The implanted device may comprise a flexible guide comprising a proximal end, a distal end, a guide body, and a stable positioning element, where the guide body defines a lumen extending from the guide proximal end to the guide distal end. A drug delivery device is removably and stably positioned within the guide lumen. The drug delivery device is positioned for delivery of drug from a drug reservoir of the drug delivery device and through the distal end of the guide lumen.
A primary object of the invention is to provide a means of closed exchange of implanted device components. An important advantage of the invention is that the internal surfaces of the implanted device are not brought into contact with the outside environment, where contamination and infection may occur. The invention is particularly useful for devices that are difficult to position and re-position, thus making it advantageous to exchange only the expended component, rather than the entire device.
These and other objects, advantages and features of the present invention will become apparent to those skilled in the art upon reading this disclosure in combination with drawings wherein like numerals refer to like components throughout.